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Resident Audio T4

Thunderbolt Audio & MIDI Interface By Sam Inglis
Published March 2015

Resident Audio’s mid-price Thunderbolt interface has some nifty tricks up its sleeve.

Apple have been giving Thunderbolt the hard sell for several years now, but uptake among audio interface manufacturers remains fairly low. No doubt this is partly due to the cost and effort involved in developing new hardware and drivers, but it also reflects the perception that Thunderbolt doesn’t seem to offer any killer advantages over established alternatives. Perhaps for this reason, most of the Thunderbolt audio interfaces that have appeared so far occupy the high end of the market, where its high data bandwidth helps to support huge I/O counts.

Nevertheless, smaller and cheaper Thunderbolt interfaces are now beginning to emerge. In December 2014, for instance, we reviewed the Zoom TAC2, a simple but high-quality device offering two-channel I/O. And the latest kid off the block is the T4, from newcomers Resident Audio. Unlike many Thunderbolt interfaces, the T4 supports both Mac OS and Windows.

Done To A T

Offering four inputs and four outputs, the T4 doesn’t tax the bandwidth of the Thunderbolt protocol, but it does exploit one of its other features. Thunderbolt connectors can supply up to 10W bus power, significantly more than USB 2 or 3, and Resident Audio have taken full advantage: despite being bus-powered with no option to connect an external PSU, the T4 provides phantom-powered mic preamps on all four inputs, not to mention a headphone output with considerably more welly than your average USB DAC.

Resident Audio T4The T4 is also unusual in offering almost no software control over its configuration. There’s no low-latency mixer utility of the type we’re accustomed to seeing from other manufacturers. Instead, input audio can be routed directly to the outputs in the analogue domain. The plus of this is that you can audition input signals with true rather than ‘near’ zero latency. The down side is that there’s no way to alter the relative levels of the four inputs in the monitor mix; all you can do is make them all louder or quieter with respect to the signal coming from your Mac.

All four inputs are on front-panel Neutrik Combo XLR/jack sockets — which, for some reason, are mounted upside-down. The unmarked and uncalibrated gain controls associated with each input are surrounded by ring-shaped indicators which glow green when an input signal is detected, amber when it gets hot and red when clipping occurs. Phantom power is globally switched, and each pair of inputs has a slide switch labelled Inst/Line. This adjusts the input sensitivity and (presumably) the impedance of the jack inputs to cater either for DI’d instruments or for line-level signals, but it also sets the panning of the inputs within the monitor path. In the Inst position, both inputs are panned centrally, but in the Line position they are hard-panned left and right. This applies even if you’ve actually connected microphones using the XLR connectors, so you have the ability to monitor stereo arrays in stereo and multi-miked mono setups in mono. However, it does mean that you can’t simultaneously connect, say, a line-level source to input 1 and a guitar to input 2.

The T4’s back panel houses MIDI I/O ports, a  Thunderbolt port, and five quarter-inch jack sockets for the headphones and line outputs.The T4’s back panel houses MIDI I/O ports, a Thunderbolt port, and five quarter-inch jack sockets for the headphones and line outputs.Two further knobs occupy the rightmost part of the front panel. The smaller of these sets the level at which the direct input signals are fed into the output; this, too, has a ring-shaped indicator LED which, oddly, indicates the presence of programme material coming back from the computer, rather than input audio. Its big brother is central to what Resident Audio describe as the T4’s ‘Smart Monitoring’ arrangements. These centre on the five TRS output sockets ranged along the back panel. One of these is a dedicated headphone output, while the role of the other four depends on what’s connected in a rather neat fashion. The designers have recognised that a second headphone output is often vital in recording sessions, so output 3 can double either as a balanced mono line out, or a stereo headphone out. It defaults to the latter, in which case the front-panel Monitor knob controls the level of both headphones. Said knob also controls the level of line outs 1/2, provided you’re only using the dedicated Phones jack — using output 3 to connect a second pair of headphones automatically mutes the main outputs, for some reason. In this mode, outputs 1/2 (if unmuted) and both headphone sockets carry the same stereo mix.

Connecting something to output 4 automatically puts the T4 into its other monitoring mode, where it is assumed that the user wishes to employ outputs 3/4 as independent line outs. In this mode, all four line outputs are removed from the control of the Monitor dial, so it now governs only the level of the dedicated headphone output, while direct contributions from the inputs are now routed only to the headphones and not to the line outs.

In Use

I have not come across any other bus-powered interface that offers four simultaneous phantom-powered preamps, and my first reaction was “Even if this actually works, it’ll surely drain a laptop battery in about five seconds.” Not so. I hooked up four different capacitor mics, fired up Pro Tools 11 and everything worked fine. What’s more, it did so for a surprisingly long time: the battery in my MacBook Air delivered a full two and a half hours’ recording, even with all four inputs consuming phantom power.

The software control panel, which is certainly nice and simple.The software control panel, which is certainly nice and simple.The knobs used to set input gain are small and have no calibration markings, so it’s not easy to be precise when matching gains across channels. According to the manual, the preamps offer only a 35dB gain range, but I’m not sure how accurate this figure is; in practice, I had no trouble recording quiet sources such as fingerstyle guitar. Sound-wise, I had no complaints about the results, which seemed eminently clear and free of unwanted noise or coloration.

There’s plenty of volume available from the headphone output, which isn’t affected when a second pair of phones is connected. Resident Audio’s Smart Monitoring works well in practice, and my only reservation is that it would be nice if the auto-muting of the main outputs when a second pair of phones is connected could be optional rather than compulsory. As it is, it would be fairly easy to end up in a situation where you were constantly connecting the phones to let a performer hear him or herself, then disconnecting them again for playback over speakers.

The zero-latency monitoring is simple but effective, and the inability to rebalance the inputs in the monitor path isn’t usually too big a deal when there are only four of them. Resident Audio’s Mac driver proved very stable (not having a Thunderbolt card installed on my PC, I wasn’t able to test it on Windows). Finally, the front-panel ‘traffic light’ signal indications are surprisingly useful — more so, in fact, than the meters in the largely redundant software control panel, which suffer from a severe lack of contrast.

Some rival desktop interfaces offer ADAT-format digital I/O to expand the channel count when required, and in this day and age, I’d have found that more of a selling point than the T4’s MIDI In and Out. But the fact remains that you can do a lot with four inputs, especially when — as here — you’re freed from the need for a mains PSU. Whether you’re recording small projects on location or mixing on the move, the Resident Audio T4 has a lot going for it.


  • Offers four mic inputs with phantom power, yet doesn’t require an external PSU.
  • Very easy to set up and use, with almost no user configuration required.
  • Good sound quality.
  • Output 3 can double as a second headphone socket.


  • Some might find the monitoring arrangements inflexible, especially the automatic muting of outputs 1/2 when a second pair of headphones is connected.
  • There’s no way of adjusting the relative balance of the inputs in the zero-latency monitoring path.


The T4 is a friendly, innovative and very useful portable recording device.


£399 including VAT.

Synthax Audio +44 (0)1727 821 870


Resident Audio +1 631 542 5270